Modular Deployment Architecture

An example showing how to compose independently developed services into arbitrary deployment components.

• Overview
• How To
• Organization
• Design
• BestPractices
• Conventions

Overview

The example uses the data types and topics used by the RTI Shapes Demo.

The example defines three services, each comprising of two interfaces.

• Square service: comprising of an interface for publication of squares, and an interface for subscription of squares

  • if/Square.xml : the service interfaces

• Circle service: comprising of an interface for publication of circles, and an interface for subscription of circles

  • if/Circle.xml : the service interfaces

• Triangle service: comprising of an interface for publication of triangles, and an interface for subscription of triangles

  • if/Triangle.xml : the service interfaces

Services can be composed to define new components. In this example, several components are defined by composing the above services, located in the directory run/.

• square_pub.sh : a component that implements the Square publication service
• triangle_sub.sh : a component that implements the Triangle subscription service
• circle_pub_triangle_pub.sh : a component that implements the Circle publication service and the Triangle publication service
• square_sub_circle_sub.sh : a component that implements the Square subscription service and the Circle subscription service
• square_pub_sub.sh : a component that implements the Square publication service and the Square subscription service

A component definition can be implemented in the programming language of choice. The example shows component implementations in C++11 and Lua.

• src/c++11/shapes : component implementations in C++11
• src/lua/shapes : component implementations in Lua

The RTI Shapes Demo can be used to visualize the data produced by the services, and to feed data into the services.

The directory structure and organization of the artifacts is described in the section Organization.

How To

Creating a new service

1. Define the data types used by the service

   1.1 Add the data types to the directory:

    res/types/
   

   For an example, look at res/types/ShapeType.idl.

   1.2 For data types defined in IDL, use rtiddsgen -convertToXml to generate the equivalent XML representation.

    cd res/types/
    make  
   

2. Define a new service interface: MyService

   2.1 Add a file res/qos/services/MyService_qos.xml by cloning the template res/template/TEMPLATE_MyService_qos.xml.

   2.2 Define all the service end-point qos policies. Use a topic_filter to specify per topic DataWriter and DataReader Qos. Reuse the common qos policy libraries defined in res/qos/common/, and expand those common libraries if appropriate. For an example, look at res/qos/services/Square_qos.xml.

   2.2 Add a file if/MyService.xml by cloning the template res/template/TEMPLATE_MyService.xml.

   2.3 Define all the service interface(s). For an example, look at if/Square.xml

   2.4 Ensure that the service interfaces are using the service qos profile for all DataWriter, DataReader, Publisher, and Subscriber entities.

3. Implement the service MyService

Implement the service in the programming language of choice. This example illustrates implementations in C++11 and Lua.

• src/c+11/shapes/ : C++11 implementation

  • Service_publisher[.hpp|cxx] implements the publication interface
  • Service_subscriber[.hpp|cxx] implements the subscription interface

• src/c+lua/shapes/ : Lua implementation (using rtiddsprototyper)

  • ServicePublisher.lua implements the publication interface
  • ServiceSubscriber.lua implements the subscription interface

Creating a new component

4. Define a new component: MyComponent

   4.1 Add a file run/MyComponent.sh by cloning the template res/template/TEMPLATE_MyComponent.sh.

   4.2 Name the component: NAME_Component

   4.3 Define the service composition:

   • BASE_NAME_Component
   • Continue defining BASE_NAME_<Service>, until you reach DeploymentIfLib::Component_Root

   For an example, look at: run/square_pub_sub.sh

   4.4 Add a file res/qos/components/MyComponent_qos.xml by cloning the template res/template/TEMPLATE_MyComponent_qos.xml.

   4.5 Define the component deployment qos policies. For an example look at res/qos/components/deployment.xml

   NOTE: Since the composition is by inheritance, the publisher and subscriber entities are not shared between the service interfaces.

5. Implement the component MyComponent

Implement the component in the programming language of choice. This example illustrates implementations in C++11 and Lua.

• src/c+11/shapes/ : C++11 implementation

  • Component_square_pub.cxx composed of the square publication service
  • Component_triangle_sub.cxx composed of the triangle publication service
  • Component_circle_pub_triangle_pub.cxx composed of the circle publication service and the triangle publication service
  • Component_square_sub_circle_sub.cxx composed of the square subscription service and the triangle subscription service
  • Component_square_pub_sub.cxx composed of the square publication service and the square subscription service

• src/lua/ : Lua implementation (using rtiddsprototyper)

  • Endpoints.lua generic component thats simply enumerates the endpoints of a components and exits; it is the default component that runs if an executable or lua script is not specified in the component launcher command line

Building a component

Generate the platform specific makefile (per platform)

cd src/c++11/shapes/
make makefile/x64Darwin17clang9.0  # look at $NDDSHOME/lib for choices

Build components:

cd src/c++11/shapes/
make

Clean components:

cd src/c++11/shapes/
make clean                        # as needed

Running a component

To run a component, use its launcher script MyComponent.sh:

./bin/MyComponent.sh [<domain_id> [<path_to_executable_or_lua_script>] [project_dir]]

The component's launcher script sets up the correct environment for running the component.

The [project_dir] is only needed if the launcher script is not located in the standard location under the run/ directory. The [project_dir] should contain the hierarchy with the relevant files:

[project_dir]/
	if/
	res/
		types/
		qos/

The [<path_to_executable_or_lua_script>] specifies the component implementation.

• A value ending in .lua is launched as a lua script within the rtiddsprototyper.
• Otherwise, it is launched as the component executable. E.g. MyComponent[.exe], rtiroutingservice[.exe], bash

Thus,

• To run rtiroutingservice with the component's environment:

    ./bin/MyComponent.sh <domain_id> <rtiroutingservice> [project_dir]
  

• To launch a shell with the component's environment:

  	./bin/MyComponent.sh <domain_id> bash [project_dir]
  

• See Demo for examples

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Author: Rajive Joshi, Real-Time Innovations Inc. Copyright (C) 2017.